Re: Why the DEBUG can't output the full string?

[Andrew Fish <afish@apple.com>]

> On Feb 1, 2018, at 8:23 AM, Laszlo Ersek <lersek@redhat.com> wrote:
> 
> On 02/01/18 10:47, krishnaLee wrote:
>> Hi,
>> For example,the follow code:
>> //-code-start
>> ConfigRequestHdr = HiiConstructConfigHdr (&mBlankDrvFormSetGuid, VariableName, PrivateData1->DriverHandle[0]);
>> Size = (StrLen (ConfigRequestHdr) + 32 + 1) * sizeof (CHAR16);
>> ConfigRequest = AllocateZeroPool (Size);
>> ASSERT (ConfigRequest != NULL);
>> AllocatedRequest = TRUE;
>> UnicodeSPrint (ConfigRequest, Size, L"%s&OFFSET=0&WIDTH=%016LX", ConfigRequestHdr, (UINT64)BufferSize);
>> FreePool (ConfigRequestHdr);
>> //-code-end
>> 
>> 
>> I add a debug message at the end of code:
>> DEBUG((EFI_D_INFO,"construct-ConfigRequest:%s",ConfigRequest));
>> DEBUG((EFI_D_INFO,"\r\n"));
>> 
>> 
>> and the output will be:
>> construct-ConfigRequest:GUID=db3b005aa15068459170ebd49e16c47c&NAME=00420044004d0079004900660072004e00560044006100740061&PATH=01041400db3b005aa15068459170ebd49e16c47c7fff0400&OFFSET=0&WIDTH=0000000000
>> 
>> 
>> If I add another debug message at the end of code:
>> DEBUG((EFI_D_INFO,"construct-ConfigRequest:"));
>> for(UINTN i=0;i<Size;i++)
>> {
>> DEBUG((EFI_D_INFO,"%c",ConfigRequest[i]));
>> }
>> DEBUG((EFI_D_INFO,"\r\n"));
>> 
>> 
>> and the output will be:
>> construct-ConfigRequest:GUID=db3b005aa15068459170ebd49e16c47c&NAME=00420044004d0079004900660072004e00560044006100740061&PATH=01041400db3b005aa15068459170ebd49e16c47c7fff0400&OFFSET=0&WIDTH=0000000000000052 pa?pr╝ <_<_ 
>> 
>> 
>> my platform:
>> win10_x64 + udk2017 + vs2015
> 
> Umm, I'm a bit confused by your query.
> 
> * First, most DebugLib instances have an internal buffer with fixed size
> (for the DebugPrint() function). If you try to log longer messages, they
> will be truncated.
> 
> For example, in "MdePkg/Library/BaseDebugLibSerialPort/DebugLib.c",
> there is:
> 
> #define MAX_DEBUG_MESSAGE_LENGTH  0x100
> 
> (I don't really understand your situation because the first debug
> message that you pasted does *not* look truncated.)
> 

WIDTH=0000000000 != WIDTH=0000000000000052 

Maybe "%016LX" is a little overkill for a width?

Thanks,

Andrew Fish

> 
> * Second, regarding the trailing garbage. You set "Size" to the number
> of *bytes* required for a NUL-terminated CHAR16 config request string,
> plus 32 CHAR16 objects. This is then correctly passed to both
> AllocateZeroPool() and UnicodeSPrint(). However, in the loop where you
> print individual CHAR16 objects, you also count up to the number of
> *bytes* -- that's incorrect, the limit should be the number of CHAR16
> objects (or the NUL-terminator, of course).
> 
> Laszlo
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